The Eldran series(エルドランシリーズ,Erudoran shirīzu?) is a toy and animation franchise begun by toy company Tomy in Japan. Tomy struck a cooperative deal with the animation studio Sunrise (known for its mecha series, most notably Gundam) to develop the new franchise to sell their toys.
The robots are suddenly entrusted to primary school children by patron saint "Eldran". they control the robots by co-operating, and confront the invaders who attempt to take over the Earth. The idea was that a school (or various places in a large town) could house the large transforming robots and their base would be the school that the kids would go to.
When the Eldran series was conceived by Tomy, Takara (who would later merge with Tomy), had begun making the Brave series or Yūsha series in Japan. The robots in each series would combine in certain ways to become a powerful robot and later new robots would be introduced that could combine with the title robot. Because of these similarities Raijin-Oh was featured in the PlayStation 2 video game; Brave Wars in Japan, along with several Brave series robots to show off their similarities and the game was made around the time Takara and Tomy had merged that prevented any copyright issues. Coincidentally, the Brave series anime shows was also animated by Sunrise and the robots from both Eldran and Yūsha had similar antennae on their heads. The main difference between Eldran and Yūsha is that the Eldran robots are all animals whereas the Yūsha robots, with some exceptions, are mostly vehicles.